Yarn support tubes formed of multiple plies of spirally wound strips of paper or paperboard are conventionally used as support members onto which yarn is wound. The outer surface of the yarn support tube is selected to have particular characteristics, in terms of smoothness, friction coefficient, etc., depending on the particular type of yarn which is to be wound onto the tube.
In the case of elastomeric yarns, which typically are treated with a finish oil or emulsion, the outer surface of the support tube may include a layer of material which is impervious to the finish emulsion so as to prevent the emulsion from migrating into the paperboard core of the tube. For example, in one known yarn support tube for elastomeric yarn, the tube is formed of a paperboard tube core made by winding several thin plies of paperboard onto a mandrel with adhesive applied to the plies, the outermost paperboard ply being printed with an ink for visually distinguishing the tube. The outermost ply of the yarn support tube comprises a film of a copolymer of vinylidene chloride and vinyl chloride such as the film sold under the trademark SARAN.RTM.. The SARAN.RTM. film layer is formed in a strip slightly wider than the paperboard plies and is wound at the same spiral wind angle as the paperboard plies such that the SARAN.RTM. strip overlaps itself at the edges to form a spiral lap joint. A water-based adhesive is applied to the lower surface of the SARAN.RTM. strip and the strip is wound onto the tube core such that the adhesive creates a film-to-film bond of the SARAN.RTM. at the spiral lap joint. As the completed tube is advanced down the mandrel, the tube is cut into so-called "parent" tubes of 40-60 inches in length. The parent tubes are stored for a time to allow the adhesive to dry, and the parent tubes are then cut to the desired finished lengths to form completed yarn support tubes. The outer SARAN.RTM. layer forms a barrier which substantially prevents finish emulsion from being wicked into the paper tube core.
Although this yarn tube construction has been used successfully for many years, it has a number of disadvantages. For instance, it takes 6 to 8 hours for the water-based adhesive at the overlapping portions of SARAN.RTM. to dry and form a strong enough bond to allow finish trimming of the parent tubes. Anything touching or rubbing the SARAN.RTM. bond before it is set can result in the tube having to be scrapped. For example, as the tube advances down the mandrel and is cut by a saw into parent tube lengths, the SARAN.RTM. bond is sometimes disturbed with the result that the tube must be scrapped. Similarly, even when the parent tube is successfully cut, the SARAN.RTM. bond is sometimes disturbed during the 6 to 8 hour drying time when the tube comes into contact with other parent tubes being dried, resulting in further scrap.
Additionally, because of the low bond strength at the SARAN.RTM. overlap during formation of the tube, the spiral tube-forming machine generally must be run at a relatively low speed in order to reduce the stresses exerted on the tube so that tube scrap can be minimized.
Furthermore, SARAN.RTM. is relatively expensive. In short, the construction of yarn tubes using the SARAN.RTM. film suffers from problems of relatively high scrap, low through-put, and high cost. Despite these problems, however, SARAN.RTM. has traditionally been used because it offers good affinity for elastomeric yarns such as LYCRA.RTM., i.e., the yarn is readily gripped by the tube during string-up when the winding of the yarn onto the tube is initiated.